The instant invention relates to herbicidal agents and to methods for the prevention of weed infestation in fields of growing crop plants and more particularly to the use of herbicidal thiadiazolyl ureas as selective herbicides capable of general overall application with discriminatory results.
1,3,4-thiadiazol-2-yl ureas have been described as herbicidal substances. In this connection the best known compound is 1-methyl-1(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-methyl urea, cf. German Pat. No. 1,816,696. This compound, however, is not very suitable as a selective weed killer, since it does not exhibit sufficient compatibility with crop plants. From the disclosure in German Pat. No. 2,044,442, there is evidence of the herbicidal effect of alkylsulfonyl-thiadiazolyl ureas which contain an alkyl radical with 1 to 3 carbon atoms. It is to be noted, however, that these compounds do not exhibit satisfactory selectivity between crop plants and weeds.
It is therefore an object of this invention to provide compounds which are selective in toxicity against undesirable weeds and grasses as compared to agricultural crops.
Another object of the invention is to provide herbicidal composition which can be applied to fields of growing crops for the purpose of killing weeds without damage to the crops.
Another object of the invention is to provide methods for the control of weeds by either pre-emergent or post-emergent application of certain alkylsulfonyl- and alkylsulfinyl-1,3,4-thiadiazolyl ureas.
Another object of the invention is to provide means and methods for control of weed growth among growing crops comprising indiscriminate application of herbicidal compounds and composition characterized by selective toxicity.